Métamorphisme et tectonique à la marge externe de la zone Sesia-Lanzo (Alpes occidentales)  [Metamorphism and tectonics at the external margin of Sesia-Lanzo Zone, Western Alps]

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Alternate Title:Metamorphism and tectonics at the external margin of Sesia-Lanzo Zone, Western Alps
Authors:Spalla, Maria Iole; Lardeaux, Jean Marc; Dal Piaz, Giorgio V.; Gosso, Guido
Author Affiliations:Primary:
Universita degli Studi di Milano, Dipartimento di Scienze della Terra, Milan, Italy
Ecole Normale Superieure de Lyon, France
Universita di Padova, Italy
Volume Title:Memorie di Scienze Geologiche
Source:Memorie di Scienze Geologiche, Vol.43, p.361-369. Publisher: Societa Cooperativa Tipografica, Padua, Italy. ISSN: 0391-8602
Publication Date:1991
Note:In French with English and Italian summaries. 37 refs.; illus., incl. geol. sketch map
Summary:Detailed study of the external Sesia-Lanzo Zone reveals that the 'Gneiss Minuti complex' (believed to be a mono-metamorphic greenschist facies unit tectonically sandwiched between the poly- metamorphic Sesia-Lanzo and the ophiolite-bearing nappes metamorphosed under eclogitic conditions) contains large volumes of the same pre-alpine paragneisses and granulite facies rocks that occur at the internal margin, in the 'Eclogitic Mica schist complex', and underwent locally the same high-P-low-T evolution of the latter. The major difference is in the amount of finite strain attained during the final stage of re-equilibration under greenschist-facies conditions. Widespread ductile zones with blasto- mylonitic character, localized between the ocean domain and the overriding continental mass, are interpreted to be the carriers of fluids facilitating the reactions that produced the greenschists, also catalyzed by deformation. These shear-zones are cut by undeformed 30 m.y. old calc-alkaline dykes. Thus the external margin of the Sesia-Lanzo zone overriding the ophiolitic piemontese domain represents a major suture reactivated at the end of the Alpine collision. [A.M.]
Subjects:Alpine Orogeny; Continental crust; Crust; Deformation; Ductile deformation; Faults; Gneisses; Greenschist; High pressure; Low temperature; Metamorphic rocks; Metamorphism; Mylonites; Nappes; Orogeny; P-T conditions; Petrography; Pressure; Schists; Shear zones; Tectonics; Temperature; Textures; Alps; Valle d'Aosta Italy; Europe; Italy; Sesia-Lanzo Zone; Southern Europe; Western Alps
Coordinates:N453000 N460000 E0080000 E0070000
Abstract Numbers:92M/4928
Record ID:2017012219
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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